The invention is generally related to the field of forming gate dielectrics for transistors in integrated circuits and more specifically to forming ultra-thin gate dielectrics.
Presently, there is a great demand for shrinking semiconductor devices to provide an increased density of devices on the semiconductor chip that are faster and consume less power. The scaling of devices in the lateral dimension requires vertical scaling as well so as to achieve adequate device performance. This vertical scaling requires the effective electrical thickness of the gate dielectric to be reduced so as to provide the required device performance.
Silicon dioxide has been the preferred gate dielectric material. However, scaling the thickness of SiO2 for gate dielectric applications has placed severe limitations on the oxidation process. Sub-angstrom uniformity across the wafer and thickness control are requirements for the advanced technologies that use these dielectrics. In order to be able to grow these layers on conventional furnaces, the process temperature has to be dropped to less than 850xc2x0 C. and the oxidant, O2, concentration has to be diluted. This results in the degradation of the electrical properties of the SiO2 dielectric as a result of the presence of a thicker interfacial layer.
The invention is an ultra-thin oxide structure and method. N2O is used as the oxidant for forming the ultra-thin oxide. The low oxidation efficiency of N2O compared to O2 allows the oxidation temperature to be raised to greater than 850xc2x0 C. while maintaining a reduced growth rate. In a preferred embodiment, hydrogen is added to improve the electrical properties of the oxide. In another embodiment of the invention, a cold wall lamp heater rapid thermal process (RTP) tool is used to form the ultra-thin oxide.
An advantage of the invention is providing a uniform and controlled method for forming a high quality ultra-thin oxide.
This and other advantages will be apparent to those of ordinary skill in the art having reference to the specification in conjunction with the drawings.